I want to install Ubuntu, and I backed up my stuff on a partition in the SSD that I'm going to be installing Ubuntu on. Is Ubuntu going to erase that partition on the SSD that I'm installing to?
Also does anyone know where to backup in case Ubuntu will erase those partitions. I don't have an external HDD or SSD.
There is an option to not erase the installation destination for Ubuntu, but it's probably not what you want.
First, Ubuntu has to be installed to a compatible file system, which your system probably doesn't have if you haven't already been using some other Linux distribution. In that case, you need to format (erase) a partition.
Also, even if you somehow had a compatible file system, the Ubuntu installer would still overwrite the space where it needs to install the system.
What you're currently describing as a "backup" is not really an acceptable backup. You need to have some other place to back up your important data. Having data duplicated on a different partition on the same drive doesn't do hardly anything to protect you from the most common causes of data loss.
That's up to you how and where you choose to do backups. We can't tell you what you need to back up and the best way to do it. You need to determine that for yourself based on your own threat model and the importance you put on your data. But you should be aware that if you don't back up your important files, or if you don't put them in a safe or redundant space, it's only a matter of when not if you're going to lose it.
You're playing with fire to not have good backups in an alternate location before installing operating systems. What if you mess up?
Assuming that you are using Windows 10 or 11 as your existing OS (a fairly reasonable assumption, I believe), then (as @Nmath points out), yes, it's likely that you will have to repartition/reformat. If so, this is a destructive operation and will erase the existing Windows partition and files.
Also fully agree with @Nmath on the backup topic. At the very least, I would recommend a purchase of one (preferably two, from different manufacturers) small USB drives to store essential files. And, of course, always test that you can restore from whatever backup solution you choose.
However, assuming Windows 10 or 11, you also have other options:
A virtual machine (e.g. VMWare, Hyper-V, VirtualBox)
My preference for running Ubuntu in Windows is to use WSL, the Windows Subsystem for Linux feature. This is a fairly lightweight feature which allows running Ubuntu (and other Linux distributions) on Windows without the overhead of a full VM. There are certain use cases (primarily development or system administration) where this is a fantastic option, but there are also areas where it is more advisable to use a virtual machine (or even a full-blown, dual-boot installation).
Assuming you are on a recent Windows release, installing Ubuntu on WSL can be as easy as opening PowerShell or CMD as an Administrator and running wsl --install.
Step By Step - Caution, Windows bootloader will be replaced by GRUB. Instructions for backup are not included in this answer.
(Your Windows install should now be available in GRUB).
